A liquid crystal display apparatus displays an image by using an electric field to adjust the light transmittance of a liquid crystal. This liquid crystal display apparatus drives the liquid crystal using the electric field formed between the pixel electrode and the common electrode arranged opposite to each other on the upper substrate and lower substrate.
The liquid crystal display apparatus includes a thin-film transistor array substrate (lower plate) and a color filter array substrate (upper plate) arranged opposite to each other; spacer beads (hereinafter referred to as “spacer” in some cases) for maintaining the cell gap constant between these two substrates; and a liquid crystal which fills the cell gap.
The thin-film transistor array substrate includes multiple signal wires, thin-film transistors, and alignment films recorded thereon for aligning the liquid crystal. The color filter array substrate contains a color filter for realizing colors, a black matrix for preventing light leakage, and an alignment film recorded thereon for aligning the liquid crystal.
According to the conventional art, this spacer is sprayed on a substrate according to the spray process and others using a spacer spraying apparatus.
However, this method of spraying tends to result in uneven distribution of spacer. Especially when the spacer is coagulated inside the display pixel, the coagulation becomes noticeable and display integrity is reduced. Such a problem occurs in the conventional method. Another problem is that, when a substrate provided with active element such as TFT is used, the TFT tends to break easily when force is applied to the substrate if a spacer lies at the projecting TFT portion.
To solve this problem, it is preferred to specify a spacer arrangement site, to avoid a TFT portion, or to arrange the spacer on a light shielding portion. Proposed solutions to this problem include the method of arranging the space by printing and the method by using an inkjet recording apparatus to supply the spacer to a specific position.
Of these methods, the method of supply using an inkjet recording apparatus ensures each spacer to be placed at an almost accurate position. Use of an inkjet head provided with multiple nozzles ensures simultaneous placing of a great number of spacers at specified positions. Thus, this method has an advantage of high productivity.
However, the aforementioned inkjet recording apparatus for emitting spacers has a disadvantage of allowing an jetting error to occur frequently, as compared with the case of conventional ink.
One of the techniques proposed so far to solve such a problem is the method of observing the state of jetting to provide maintenance. Examples include the method of observing the jetting of spacers with a camera and cleaning the head (Japanese Unexamined Patent Application Publication No. 11-316380) and the method of detecting early the status of spacers being coated, whereby required repair work is performed (Japanese Unexamined Patent Application Publication No. 2007-25334).
The inkjet recording apparatus for jetting spacer is required to use the ink containing large-sized spacer beads normally having a diameter of several microns, unlike the conventional color ink, and jet the spacer. Accordingly, mist or satellite tends to be produced at the time of jetting, as compared to the conventional ink. This causes the ink droplets to vibrate and requires some measures to be taken to ensure stable jetting of ink droplets.